We are investigating the structure and function of the envelope glycoproteins of murine leukemia viruses (MuLV's). The number of glycosylation sites and the structure of the oligosaccharides of MuLV's of various host range classes are being compared. In addition, we are determining the structure of the oligosaccharides linked to intracellular precursors of MuLV glycoproteins. We are also attempting to identify and characterize additional gene products of arenaviruses, and to characterize the RNA species present in defective interfering Tacaribe virus particles. Approaches to be used to identify nonstructural proteins and precursor proteins include use of high salt or heat-inactivated frog virus 3 to suppress the background of host cell synthesis, attempts to develop a coupled transcription-translation system, and analysis of products of in vitro translation directed by polysomes or poly-A containing RNA from infected cells by immune precipitation and gel electrophoresis.